Steen Moeller

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David Seamon

Kansas State University

Vsevolod Kapatsinski

University of Oregon

Maro G Machizawa

Hiroshima University

Jan A Kozák

Charles University, Prague

George Christodoulides

Université de Mons

rudolph bauer

Washington Center for Consciousness Studies

Stefka G Eriksen

University of Oslo

Oladosu A Ojengbede

University of Ibadan Nigeria

Neda Laiteerapong

University of Chicago

Dragos Simandan

Brock University

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Papers by Steen Moeller

2D Pulses using spatially dependent frequency sweeping

Magnetic Resonance in Medicine, 2015

To introduce a method of designing two-dimensional (2D) frequency-modulated pulses that produce p... more To introduce a method of designing two-dimensional (2D) frequency-modulated pulses that produce phase coherence in a spatiotemporal manner. Uniquely, this class of pulses provides the ability to compensate for field inhomogeneity using a spatiotemporally dependent trajectory of maximum coherence in a single-shot. A pulse design method based on a k-space description is developed. Bloch simulations and phantom experiments are used to demonstrate sequential spatiotemporal phase coherence and compensation for B1+ and B0 inhomogeneity. In the presence of modulated gradients, the 2D frequency-modulated pulses were shown to excite a cylinder in a selective manner. With a surface coil transmitter, compensation of the effect of B1+ inhomogeneity was experimentally verified, in agreement with simulation results. In addition, simulations were used to demonstrate partial compensation for B0 inhomogeneity. The 2D frequency-modulated pulses are a new class of pulses that generate phase coherence sequentially along a spatial trajectory determined by gradient- and frequency-modulated functions. By exploiting their spatiotemporal nature, 2D frequency-modulated pulses can compensate for spatial variation of the radiofrequency field in a single-shot excitation. Preliminary results shown suggest extensions might also be used to compensate for static field inhomogeneity. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

Simultaneous multislice imaging in dynamic cardiac MRI at 7T using parallel transmission

Magnetic Resonance in Medicine, 2016

Cardiac MRI at 7T suffers from contrast heterogeneity that can be mitigated with parallel transmi... more Cardiac MRI at 7T suffers from contrast heterogeneity that can be mitigated with parallel transmission (pTX) and, when performed during breath-hold, from a limited number of slices that can be multiplied with multiband (MB) radiofrequency pulses by simultaneous excitation of multiple slices (SMS). The goal of this study was to apply both approaches simultaneously. Using a 16-channel transmit/receive body coil, pTX SMS was applied with/without CAIPIRINHA with a modified gradient echo cine sequence. Different calibration schemes were investigated for the slice-GRAPPA reconstruction kernels as a function of the cardiac cycle. Excellent slice separation for MB = 2 was achieved with CAIPIRINHA, with slice leakage values below 3% for 99% of all voxels. A critical finding of this study was the variation of the MB leakage factor in the heart by as much as 30% throughout the cardiac cycle, which was reduced greatly when reconstruction kernels were calibrated on multiple cardiac phases. Acceptable results were still obtained when applying further acceleration with MB = 3 in combination with in-plane GRAPPA. In one case, two-spoke pulses were compared with one-spoke pulses, resulting as expected in improved homogeneity. pTX SMS imaging at 7T can address contrast heterogeneity while allowing larger slice coverage in cardiac MRI performed under breath-hold. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

Frequency Swept Excitation for Magnetic Resonance

Three dimensional RF coil structures for field profiling

Dipole matched filter for MRI

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Generalized Fourier Transforms Classes

Http Dx Doi Org 10 1080 10652460213530, Oct 18, 2010

Multi-Current Elements for Magnetic Resonance Radio Frequency Coils

Phase-cycled simultaneous multislice balanced SSFP imaging with CAIPIRINHA for efficient banding reduction

Magnetic resonance in medicine, Jan 15, 2015

To present a time-efficient technique for banding reduction in balanced steady-state free precess... more To present a time-efficient technique for banding reduction in balanced steady-state free precession (bSSFP) imaging using phase-cycled simultaneous multislice (SMS) acquisition with CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration). The proposed technique exploits the inherent phase modulation of SMS imaging with CAIPIRINHA to acquire multiple phase-cycled images, which can be combined for efficient banding reduction within the same scan time of a single-band bSSFP scan. Bloch equation simulation, phantom and in vivo brain, abdominal and cardiac imaging experiments were performed on healthy volunteers at 3T using multi-channel head and body array coils with SMS acceleration factors of two to four. The performance of banding reduction was quantitatively evaluated based on the percent ripple of signal distribution and signal-to-noise ratio (SNR) efficiency in both phantom and human studies. The banding artifact was successfully removed or suppressed ...

Multichannel diffusion MR image reconstruction: how to reduce elevated noise floor and improve fiber orientation estimation

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Comparison of simultaneous Multiband whole brain imaging with Multiplexed-EPI

Evaluation of 2D multiband EPI imaging for high-resolution, whole-brain, task-based fMRI studies at 3T: Sensitivity and slice leakage artifacts

NeuroImage, 2015

Functional magnetic resonance imaging (fMRI) studies that require high-resolution whole-brain cov... more Functional magnetic resonance imaging (fMRI) studies that require high-resolution whole-brain coverage have long scan times that are primarily driven by the large number of thin slices acquired. Two-dimensional multiband echo-planar imaging (EPI) sequences accelerate the data acquisition along the slice direction and therefore represent an attractive approach to such studies by improving the temporal resolution without sacrificing spatial resolution. In this work, a 2D multiband EPI sequence was optimized for 1.5mm isotropic whole-brain acquisitions at 3T with 10 healthy volunteers imaged while performing simultaneous visual and motor tasks. The performance of the sequence was evaluated in terms of BOLD sensitivity and false-positive activation at multiband (MB) factors of 1, 2, 4, and 6, combined with in-plane GRAPPA acceleration of 2× (GRAPPA 2), and the two reconstruction approaches of Slice-GRAPPA and Split Slice-GRAPPA. Sensitivity results demonstrate significant gains in temporal signal-to-noise ratio (tSNR) and t-score statistics for MB 2, 4, and 6 compared to MB 1. The MB factor for optimal sensitivity varied depending on anatomical location and reconstruction method. When using Slice-GRAPPA reconstruction, evidence of false-positive activation due to signal leakage between simultaneously excited slices was seen in one instance, 35 instances, and 70 instances over the ten volunteers for the respective accelerations of MB 2×GRAPPA 2, MB 4×GRAPPA 2, and MB 6×GRAPPA 2. The use of Split Slice-GRAPPA reconstruction suppressed the prevalence of false positives significantly, to 1 instance, 5 instances, and 5 instances for the same respective acceleration factors. Imaging protocols using an acceleration factor of MB 2×GRAPPA 2 can be confidently used for high-resolution whole-brain imaging to improve BOLD sensitivity with very low probability for false-positive activation due to slice leakage. Imaging protocols using higher acceleration factors (MB 3 or MB 4×GRAPPA 2) can likely provide even greater gains in sensitivity but should be carefully optimized to minimize the possibility of false activations.

Unbiased T1 Weighted Images at High Field without Signal Variation due to receive B1 field, T2* and Proton Density

Quantitative evaluation of Multi-channel fMRI at 7 Tesla with high 1–dimensional reduction factors

Parallel Imaging (SENSE) of the human head with one dimensional reduction (and maximum aliasing) ... more Parallel Imaging (SENSE) of the human head with one dimensional reduction (and maximum aliasing) factors of four can be performed at very high fields (7 Tesla) with low g-factors (average and maximal). In this study, consequences of the use of such a large 1-dimensional reduction and maximum aliasing factor in EPI based fMRI studies conducted at 7 Tesla was examined quantitatively.

Simultaneous Multi-Slice Parallel RF Excitation with In-Plane B1+ Homogenization

B1 phase spatial pattern at 7 Tesla: impact on B1 inhomogeneities with a head transceive transmission line array coil

Simultaneous multi-slice Turbo-FLASH imaging with CAIPIRINHA for whole brain distortion-free pseudo-continuous arterial spin labeling at 3 and 7 T

NeuroImage

Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial... more Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label, improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 Tesla. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of stan...

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Introduction to SWIFT (Sweep Imaging with Fourier Transformation) for Magnetic Resonance Imaging of Materials

MRS Proceedings, 2006

A novel, fast, and quiet method of magnetic resonance imaging (MRI), called SWIFT (sweep imaging ... more

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Simultaneous Multi-slice Turbo-FLASH Imaging with CAIPIRINHA for Whole Brain Distortion-Free Pseudo-Continuous Arterial Spin Labeling at 3 and 7T

NeuroImage, Jan 30, 2015

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Theoretical and experimental evaluation of multi-band EPI for high-resolution whole brain pCASL Imaging

NeuroImage, 2015

Multi-band echo planar imaging (MB-EPI), a new approach to increase data acquisition efficiency a... more Multi-band echo planar imaging (MB-EPI), a new approach to increase data acquisition efficiency and/or temporal resolution, has the potential to overcome critical limitations of standard acquisition strategies for obtaining high-resolution whole brain perfusion imaging using arterial spin labeling (ASL). However, the use of MB also introduces confounding effects, such as spatially varying amplified thermal noise and leakage contamination, which have not been evaluated to date as to their effect on cerebral blood flow (CBF) estimation. In this study, both the potential benefits and confounding effects of MB-EPI were systematically evaluated through both simulation and experimentally using a pseudo-continuous arterial spin labeling (pCASL) strategy. These studies revealed that the amplified noise, given by the geometry factor (g-factor), and the leakage contamination, assessed by the total leakage factor (TLF), have a minimal impact on CBF estimation. Furthermore, it is demonstrated t...

Heritability of Fractional Anisotropy in Human White Matter: A Comparison of Human Connectome Project and ENIGMA-DTI Data

by Anderson Winkler, Jesper Andersson, Stamatios Sotiropoulos, Jessika Sussmann, Katie McMahon, and Steen Moeller

NeuroImage, Jan 3, 2015

The degree to which genetic factors influence brain connectivity is beginning to be understood. L... more The degree to which genetic factors influence brain connectivity is beginning to be understood. Large-scale efforts are underway to map the profile of genetic effects in various brain regions. The NIH-funded Human Connectome Project (HCP) is providing data valuable for analyzing the degree of genetic influence underlying brain connectivity revealed by state-of-the-art neuroimaging methods. We calculated the heritability of the fractional anisotropy (FA) measure derived from diffusion tensor imaging (DTI) reconstruction in 481 HCP subjects (194/287M/F) consisting of 57/60 pairs of mono- and dizygotic twins, and 246 siblings. FA measurements were derived using (Enhancing NeuroImaging Genetics through Meta-Analysis) ENIGMA DTI protocols and heritability estimates were calculated using the SOLAR-Eclipse imaging genetic analysis package. We compared heritability estimates derived from HCP data to those publicly available through the ENIGMA-DTI consortium, which were pooled together from ...

2D Pulses using spatially dependent frequency sweeping

Magnetic Resonance in Medicine, 2015

Simultaneous multislice imaging in dynamic cardiac MRI at 7T using parallel transmission

Magnetic Resonance in Medicine, 2016

Frequency Swept Excitation for Magnetic Resonance

Three dimensional RF coil structures for field profiling

Dipole matched filter for MRI

Download

Generalized Fourier Transforms Classes

Http Dx Doi Org 10 1080 10652460213530, Oct 18, 2010

Multi-Current Elements for Magnetic Resonance Radio Frequency Coils

Phase-cycled simultaneous multislice balanced SSFP imaging with CAIPIRINHA for efficient banding reduction

Magnetic resonance in medicine, Jan 15, 2015

Multichannel diffusion MR image reconstruction: how to reduce elevated noise floor and improve fiber orientation estimation

Download

Comparison of simultaneous Multiband whole brain imaging with Multiplexed-EPI

Evaluation of 2D multiband EPI imaging for high-resolution, whole-brain, task-based fMRI studies at 3T: Sensitivity and slice leakage artifacts

NeuroImage, 2015

Unbiased T1 Weighted Images at High Field without Signal Variation due to receive B1 field, T2* and Proton Density

Quantitative evaluation of Multi-channel fMRI at 7 Tesla with high 1–dimensional reduction factors

Simultaneous Multi-Slice Parallel RF Excitation with In-Plane B1+ Homogenization

B1 phase spatial pattern at 7 Tesla: impact on B1 inhomogeneities with a head transceive transmission line array coil

Simultaneous multi-slice Turbo-FLASH imaging with CAIPIRINHA for whole brain distortion-free pseudo-continuous arterial spin labeling at 3 and 7 T

NeuroImage

Download

Introduction to SWIFT (Sweep Imaging with Fourier Transformation) for Magnetic Resonance Imaging of Materials

MRS Proceedings, 2006

A novel, fast, and quiet method of magnetic resonance imaging (MRI), called SWIFT (sweep imaging ... more

Download

Simultaneous Multi-slice Turbo-FLASH Imaging with CAIPIRINHA for Whole Brain Distortion-Free Pseudo-Continuous Arterial Spin Labeling at 3 and 7T

NeuroImage, Jan 30, 2015

Download

Theoretical and experimental evaluation of multi-band EPI for high-resolution whole brain pCASL Imaging

NeuroImage, 2015

Heritability of Fractional Anisotropy in Human White Matter: A Comparison of Human Connectome Project and ENIGMA-DTI Data

by Anderson Winkler, Jesper Andersson, Stamatios Sotiropoulos, Jessika Sussmann, Katie McMahon, and Steen Moeller

NeuroImage, Jan 3, 2015

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